A hybrid vehicle efficiently combines two or more distinct power sources. In general, the hybrid vehicle combines an internal combustion engine which obtains rotational force by combusting a fuel, and one or more electric motors which obtain rotational force from electrical energy of a battery.
Power transmission of the hybrid vehicle may be variously configured with the engine and the motor, and the most common power transmission is a parallel power transmission or a serial power transmission.
The hybrid vehicle may output optimum output torque according to synchronization of the engine and the motor by utilizing two power sources, that is, the engine and the motor.
The hybrid vehicle can travel in an electric vehicle (EV) mode that is a pure electric vehicle mode using only power from the motor or in a hybrid electric vehicle (HEV) mode which uses both power from the engine and power from the motor.
During braking of the vehicle or coasting of the vehicle by inertia, braking and inertia energy is collected through generation of the motor in a regenerative braking (RB) mode.
A typical hybrid vehicle drive train has an engine clutch installed between the engine and the motor. The engine, the engine clutch, the motor (driving motor), and a transmission are sequentially arranged. A battery is connected to the motor to be charged/discharged through a power converter.
FIGS. 1 and 2 are diagrams illustrating main configurations of a hybrid vehicle including two motors (MG1 and MG2) 3 and 5. An engine clutch 2 is interposed between an engine 1 and the first motor (MG1) 3 driving the vehicle. The engine 1 and the first motor (MG1) 3 are mechanically connected by the engine clutch 2 to transmit power or are disconnected to block the power transmission between the first motor 3 and the engine 1.
The first motor 3 is mechanically connected to a wheel 9 of the vehicle through a transmission 8 to transmit the power. When both of the engine 1 and the first motor 3 are driven, the power may be transmitted to the wheel 9 through the transmission 8.
The second motor (MG2) 5 is mechanically connected to the engine 1 through a belt and the like to transmit the power. The hybrid vehicle further includes a first inverter 4 for driving the first motor 3 and a second inverter 6 for driving the second motor 5. The first inverter 4 and the second inverter 6 are connected to a high voltage battery (main battery) 10 through a DC-link terminal 7 having a capacitor C.
The first inverter 4 and the second inverter 6 supply regenerative power by the motors 3 and 5 while the motors 3 and 5 are regenerated through the DC-link terminal 7, or receive power from the high voltage battery 10 through the DC-link terminal 7 for driving the motors 3 and 5.
High voltage components, such as a low voltage DC to DC converter (LDC) 13, an air compressor (A/C) 15, and an electronic oil pump (EOP) 16 which will be described below, as well as the first inverter 4 and the second inverter 6, receive high voltage power through the DC-link terminal 7.
A main relay 11 for selectively supplying/blocking the power of the high voltage battery 10 is mechanically connected between the high voltage battery 10 and the DC-link terminal 7 to block the power supply between the high voltage battery 10 and the DC-link terminal 7. The main relay 11 is controlled to be on/off by a battery management system (BMS) 12, and the high voltage battery 10 supplies or receives and stores the power through the main relay 11.
A low voltage battery (auxiliary battery) 14 of 12V and a low voltage electronic load (not illustrated) are connected through the LDC 13. The high voltage components such as the A/C 15 and the EOP 16 are connected to the DC-link terminal 7 so as to receive the power from the high voltage battery 10.
The LDC 13 in the hybrid vehicle serves as an alternator for a conventional gasoline engine, and converts the power between the high voltage power supply and the low voltage electronic load (the low voltage battery or other low voltage electronic loads within the vehicle). The LDC 13 further steps down a DC voltage of the high voltage power supply within the vehicle such as the high voltage battery 10 and supplies the step-down voltage to the low voltage battery 14 and other low voltage electronic loads.
That is, the LDC 13 converts the high voltage DC voltage from the high voltage battery 10 and the high direct voltage of regenerative energy of the motors 3 and 4 to charge the low voltage battery 14 with the converted voltage or supply the converted voltage to the low voltage electronic loads.
When the main relay 11, which provides a high voltage between the high voltage battery 10 and the DC-link terminal 7, the inverters 4 and 6, is abnormally off while the hybrid vehicle is running, the inverters 4 and 6 cannot receive the high voltage and thus cannot function properly.
The LDC 13 also cannot receive the high voltage, and thus, it is impossible to charge the low voltage battery 14, and the LDC 13 cannot supply power to the low voltage electronic load.
In this case, the low voltage (12V) electronic load continuously consumes the power from the low voltage battery 14, and as a result, the low voltage battery 14 is discharged.
Particularly, when the low voltage battery 14 is discharged when the vehicle is running, controllers receiving the power from the low voltage battery 14 in the vehicle stop operating.
For example, when the low voltage battery 14 is discharged to a predetermined voltage or lower, a control power supply of a motor driven power steering (MDPS) device of a vehicle is turned off, and thus, a steering wheel locking occurs when the low voltage battery 14 is discharged.
When the high voltage main relay 12 is turned off, other various high voltage components such as the A/C 15 and the EOP 16 which receive the power from the high voltage battery 10 stop operating. If the EOP 16, which supplies hydraulic pressure to the transmission 8, does not function, hydraulic pressure is not formed within the transmission 8 so that it is impossible to operate the vehicle.
In contrast to a vehicle using both a mechanical oil pump and an electronic oil pump, when the main relay does not function properly in a vehicle having only a high voltage electronic oil pump due to failure of another high voltage component while the vehicle is running, the electronic oil pump cannot also receive a driving power source so that it is impossible to form hydraulic pressure within the transmission and operate the vehicle.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.